We search for a qualitative estimation of the pressures induced by surface tension in the generations of the airway tree.
The geometry of the bronchial tree is approximated with a cascade of bifurcating cylindrical airways [1]}, [2]}, see Fig. REF .
The airways are numbered by using a generation index \(i\)  that represents the number of bifurcations from the root of the tree, i.e. the trachea, to the considered airway.
We assume that the dimensions of the airways between two consecutive generations are related by a homothetic factor \(h\) , independent of the generation index.
The theoretical value \(h = (1/2)^{1/3} \simeq 0.79\)  has been found to represent adequately the geometry of the mammal lung [3]}, [4]}, [2]}, [6]}, [7]}, [8]}.
